Organic compounds

ABSTRACT

The present invention relates to certain PDE2 inhibitory compounds, in free or salt form, pharmaceutical compositions containing such compounds and methods for the treatment of PDE2 mediated disorders.

TECHNICAL FIELD

The present invention relates to PDE2 inhibitory compounds of Formula Ias described below, their use as pharmaceuticals and pharmaceuticalcompositions comprising them. These compounds are useful e.g., in thetreatment of PDE2-mediated disorders such as anxiety, depression, autismspectrum disorder (ASD), schizophrenia and cognitive impairment.

BACKGROUND OF THE INVENTION

PDE2 is a 105-KDa homodimer that is expressed in a wide variety oftissues and cell types including brain (including hippocampus, striatumand prefrontal cortex), heart, platelets, endothelial cells, adrenalglomerulosa cells and macrophages. Although cGMP is the preferredsubstrate and effector molecule for this enzyme, PDE2 hydrolyzes bothcyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate(cGMP) and is thought to be involved in a number of physiologicalprocesses. In particular, it has been shown that inhibition of nitricoxide synthase (NOS), which reduces cGMP signaling, attenuates thebehavioral effects of the benzodiazepine chlordiazepoxide, an anxiolyticcompound. Also, commercially-available tool inhibitors of PDE2 such asBay 60-7550 have been shown to increase cyclic nucleotide levels in thebrain and have significant anti-anxiety and anti-depressant effects innormal and stressed rodents (Xu et al., Eur. J. Pharmacol. (2005)518:40-46; Masood et al., J. Pharmacol. Exp. Ther. (2008) 326:369-379;Masood et al., JPET (2009) 331:690-699; Xu et al., Intl. J.Neuropsychopharmacol. (2013) 16:835-847). Inhibition of PDE2 by Bay60-7550 has also been shown to elevate cGMP and cAMP levels instimulated primary neuronal cultures in a dose responsive manner;enhance LTP in hippocampal slice preparations in response to electricalstimulation; enhance learning in novel object recognition animal modeland a social recognition task in rats; improve acquisition andconsolidation phases of novel object memory in age impaired rats;improve performance on object location and recognition tasks whenadministered after training. Gomez et al., Bioorg. Med. Chem. Lett.(2013) 23:6522-6527. Bay 60-7550 has also been shown to improvecognition and memory function in rats through the enhancement of nNOSactivity in the brain. (Domek-Lopacinska et al. (2008) Brain Res.1216:68-77). Therefore, PDE2 plays an important role in effectivebehaviors and cognitive function.

In addition to effective behavior and cognitive function, it has beenobserved that in endothelial cells, PDE2A mRNA and activity are highlyinduced in response to tumor necrosis factor-α stimulation in vitro.Selective inhibition of PDE2 activity with9-(6-phenyl-2-oxohex-3-yl)-2-(3,4-dimethoxybenzyl)-purin-6-one (PDP)greatly alters the barrier function of endothelial cells, suggestingthat PDE2 is likely to play an important role in regulating fluid andprotein integrity of the circulatory system under pathologicalconditions. Therefore, PDE2 may be a good pharmacological target forsepsis or in more localized inflammatory responses.

In a recent study, PDE2 inhibition has also been shown to elicitpulmonary dilation, prevents pulmonary vascular remodeling and reducesthe right ventricular hypertrophy characteristic of pulmonaryhypertension, suggesting therapeutic potential of PDE2 inhibition inpulmonary hypertension. Bubb et al., “Inhibition of Phosphodiesterase 2Augments cGMP and cAMP Signaling to Ameliorate Pulmonary Hypertension”,Circulation, Aug. 5, 2014, p. 496-507, DOI:10.1161/CIRCULATIONAHA.114.009751.

Despite the promising preclinical data and the identification of PDE2 asa promising drug target, no PDE2 inhibitors are currently known to beunder clinical investigation due in part to the poor metabolic stabilityand brain penetrance of existing PDE2 compounds. There is thus a needfor compounds that selectively inhibit PDE2 activity while demonstratesuperior biophysical properties.

SUMMARY OF THE INVENTION

The disclosure provides novel compounds having potent and selective PDE2inhibitory properties with improved orally availability and brainaccess. Therefore, in the first aspect, the disclosure provides acompound of Formula I:

wherein

-   -   (i) R₁ is C₁₋₄alkyl (e.g., methyl);    -   (ii) R₂ is selected from the group consisting of:        -   H,        -   —OH,        -   halo (e.g., chloro),        -   C₁₋₄alkyl (e.g., methyl),        -   C₁₋₄alkoxy (e.g., methoxy or ethoxy),        -   —N(R_(f))(R_(g)),        -   —C(O)N(R_(h))(R_(i)),        -   —C(O)OR_(j),        -   —CN,        -   C₁₋₄alkylthio (e.g., ethylthio),        -   heteroaryl (e.g., pyrazolyl, e.g., pyrazol-1-yl),        -   heteroC₃₋₇cycloalkyl (e.g., morpholinyl (e.g.,            morpholin-1-yl) or pyrrolidinyl (e.g., pyrrolidin-1-yl)),            and        -   aryloxy (e.g., phenoxy) wherein said aryl is optionally            substituted with one or more halo (e.g., fluoro), for            example 4-fluorophenoxy;    -   (iii) R₃ is H or C₁₋₄alkyl (e.g., methyl);    -   (iv) R_(a), R_(b), R_(c), R_(d) and R_(e) are independently H,        halo (e.g., chloro or fluoro), —O—C₁₋₆alkyl (e.g., propoxy,        butoxy (e.g., n-butoxy, isobutoxy), —OCH₂-cyclopropyl,        —OCH₂-cyclobutyl or —OCH₂-cyclopentyl);    -   (v) R_(f) and R_(g) are independently H, C₁₋₄alkyl (e.g.,        methyl) or heteroaryl (e.g., pyridyl (e.g., pyrid-2-yl));    -   (vi) R_(h) and R_(i) are independently H or C₁₋₄alkyl (e.g.,        ethyl);    -   (vii) R_(j) is H or C₁₋₄alkyl (e.g., ethyl);        in free or salt form.

The disclosure further provides the compound of Formula I as follows:

-   -   1.1 Formula I, wherein R₁ is C₁₋₄alkyl (e.g., methyl);    -   1.2 Formula 1.1, wherein R₁ is methyl;    -   1.3 Formula I, or any of 1.1-1.2, wherein R₂ is selected from        the group consisting of H; —OH; halo (e.g., chloro); C₁₋₄alkyl        (e.g., methyl); C₁₋₄alkoxy (e.g., methoxy or ethoxy);        —N(R_(f))(R_(g)); —C(O)N(R_(h))(R_(i)); —C(O)OR_(j); —CN;        C₁₋₄alkylthio (e.g., ethylthio); heteroaryl (e.g., pyrazolyl,        e.g., pyrazol-1-yl); heteroC₃₋₇cycloalkyl (e.g., morpholinyl        (e.g., morpholin-1-yl) or pyrrolidinyl (e.g., pyrrolidin-1-yl));        and aryloxy (e.g., phenoxy) wherein said aryl is optionally        substituted with one or more halo (e.g., fluoro), for example        4-fluorophenoxy;    -   1.4 Formula I, or any of 1.1-1.2, wherein R₂ is H;    -   1.5 Formula I, or any of 1.1-1.2, wherein R₂ is —OH;    -   1.6 Formula I, or any of 1.1-1.2, wherein R₂ is halo (e.g.,        chloro);    -   1.7 Formula I, or any of 1.1-1.2, wherein R₂ is chloro;    -   1.8 Formula I, or any of 1.1-1.2, wherein R₂ is C₁₋₄alkyl (e.g.,        methyl);    -   1.9 Formula I, or any of 1.1-1.2, wherein R₂ is methyl;    -   1.10 Formula I, or any of 1.1-1.2, wherein R₂ is C₁₋₄alkoxy        (e.g., methoxy or ethyoxy);    -   1.11 Formula I, or any of 1.1-1.2, wherein R₂ is methoxy;    -   1.12 Formula I, or any of 1.1-1.2, wherein R₂ is ethoxy;    -   1.13 Formula I, or any of 1.1-1.2, wherein R₂ is        N(R_(f))(R_(g));    -   1.14 Formula I or 1.13, wherein R_(f) and R_(g) are        independently H, C₁₋₄alkyl (e.g., methyl) or heteroaryl (e.g.,        pyridyl (e.g., pyrid-2-yl));    -   1.15 Formula I or 1.13, wherein R_(f) is H and R_(g) is selected        from H, C₁₋₄alkyl (e.g., methyl) or heteroaryl (e.g., pyridyl        (e.g., pyrid-2-yl));    -   1.16 Formula I or 1.13, wherein R_(f) is H and R_(g) is pyridyl        (e.g., pyrid-2-yl);    -   1.17 Formula I or 1.13, wherein R_(f) is H and R_(g) is        C₁₋₄alkyl (e.g., methyl);    -   1.18 Formula I or 1.13, wherein R_(f) is H and R_(g) is methyl;    -   1.19 Formula I or 1.13, wherein R_(f) and R_(g) are both H;    -   1.20 Formula I or 1.13, wherein R_(f) and R_(g) are both        C₁₋₄alkyl (e.g., methyl);    -   1.21 Formula I or 1.13, wherein R_(f) and R_(g) are both methyl;    -   1.22 Formula I or 1.13, wherein R_(f) is H and R_(g) is        heteroaryl (e.g., pyridyl (e.g., pyrid-2-yl));    -   1.23 Formula I or 1.13, wherein R₂ is —C(O)N(R_(h))(R_(i)),    -   1.24 Formula I or 1.23, wherein R_(h) and R_(i) are        independently H or C₁₋₄alkyl (e.g., ethyl);    -   1.25 Formula I or 1.23, wherein R_(h) is H and R_(i) is H or        C₁₋₄alkyl (e.g., ethyl);    -   1.26 Formula I or 1.23, wherein R_(h) is H and R_(i) is        C₁₋₄alkyl (e.g., ethyl)    -   1.27 Formula I or 1.23, wherein R_(h) is H and R_(i) is ethyl;    -   1.28 Formula I or 1.23, wherein R_(h) and R_(i) are both H;    -   1.29 Formula I, or any of 1.1-1.2, wherein R₂ is —C(O)OR_(j);    -   1.30 Formula I or 1.29, wherein R_(j) is H or C₁₋₄alkyl (e.g.,        ethyl);    -   1.31 Formula I or 1.29, wherein R_(j) is H;    -   1.32 Formula I or 1.29, wherein R_(j) is C₁₋₄alkyl (e.g.,        ethyl);    -   1.33 Formula I or 1.29, wherein R_(j) is ethyl;    -   1.34 Formula I, or any of 1.1-1.2, wherein R₂ is —CN;    -   1.35 Formula I, or any of 1.1-1.2, wherein R₂ is C₁₋₄alkylthio        (e.g., ethylthio);    -   1.36 Formula I, or any of 1.1-1.2, wherein R₂ is ethylthio;    -   1.37 Formula I, or any of 1.1-1.2, wherein R₂ is heteroaryl        (e.g., pyrazolyl, e.g., pyrazol-1-yl);    -   1.38 Formula I, or any of 1.1-1.2, wherein R₂ is pyrazolyl,        e.g., pyrazol-1-yl;    -   1.39 Formula I, or any of 1.1-1.2, wherein R₂ is        heteroC₃₋₇cycloalkyl (e.g., morpholinyl (e.g., morpholin-1-yl)        or pyrrolidinyl (e.g., pyrrolidin-1-yl));    -   1.40 Formula I, or any of 1.1-1.2, wherein R₂ is        heteroC₅₋₆cycloalkyl;    -   1.41 Formula I, or any of 1.1-1.2, wherein R₂ is morpholinyl        (e.g., morpholin-1-yl);    -   1.42 Formula I, or any of 1.1-1.2, wherein R₂ is pyrrolidinyl        (e.g., pyrrolidin-1-yl);    -   1.43 Formula I, or any of 1.1-1.2, wherein R₂ is aryloxy (e.g.,        phenoxy) wherein said aryl is optionally substituted with one or        more halo (e.g., fluoro), for example 4-fluorophenoxy;    -   1.44 Formula I, or any of 1.1-1.2, wherein R₂ is phenoxy wherein        said phenyl is optionally substituted with one or more halo        (e.g., fluoro), for example 4-fluorophenoxy;    -   1.45 Formula I, or any of 1.1-1.2, wherein R₂ is        4-fluorophenoxy;    -   1.46 Formula I or any of 1.1-1.45, wherein R₃ is H or C₁₋₄alkyl        (e.g., methyl);    -   1.47 Formula I or any of 1.1-1.45, wherein R₃ is H;    -   1.48 Formula I or any of 1.1-1.45, wherein R₃ is C₁₋₄alkyl        (e.g., methyl);    -   1.49 Formula I or any of 1.1-1.45, wherein R₃ is methyl;    -   1.50 Formula I or any of 1.1-1.49, wherein R_(a), R_(b), R_(c),        R_(d) and R_(e) are independently H, halo (e.g., chloro or        fluoro), —O—C₁₋₆alkyl (e.g., propoxy, butoxy (e.g., n-butoxy,        isobutoxy), —OCH₂-cyclopropyl, —OCH₂-cyclobutyl or        —OCH₂-cyclopentyl);    -   1.51 Formula I or any of 1.1-1.50, wherein R_(a), R_(b), R_(c),        R_(d) and R_(e) are independently H;    -   1.52 Formula I or any of 1.1-1.51, wherein R_(a), R_(b), R_(c),        R_(d) and R_(e) are independently halo (e.g., chloro or fluoro);    -   1.53 Formula I or any of 1.1-1.51, wherein R_(a), R_(b), R_(c),        R_(d) and R_(e) are independently chloro or fluoro;    -   1.54 Formula I or any of 1.1-1.53, wherein R_(a), R_(b), R_(c),        R_(d) and R_(e) are independently —O—C₁₋₆alkyl (e.g., propoxy,        butoxy (e.g., n-butoxy, isobutoxy), —OCH₂-cyclopropyl,        —OCH₂-cyclobutyl or —OCH₂-cyclopentyl);    -   1.55 Formula I or any of 1.1-1.53, wherein R_(a), R_(b), R_(c),        R_(d) and R_(e) are independently —O—C₃₋₆alkyl;    -   1.56 Formula I or any of 1.1-1.55, wherein R_(b), R_(c) and        R_(e) are all H;    -   1.57 Formula I or any of 1.1-1.56, wherein R_(b), R_(c) and        R_(e) are all H; and R_(a) and R_(d) are independently selected        from H, halo (e.g., chloro or fluoro), —O—C₁₋₆alkyl (e.g.,        propoxy, butoxy (e.g., n-butoxy, isobutoxy), —OCH₂-cyclopropyl,        —OCH₂-cyclobutyl or —OCH₂-cyclopentyl);    -   1.58 Formula I or any of 1.1-1.56, wherein R_(b), R_(c) and        R_(e) are all H; R_(a) is halo (e.g., chloro or fluoro); and        R_(d) is H, halo (e.g., chloro or fluoro) or —O—C₁₋₆alkyl (e.g.,        propoxy, butoxy (e.g., n-butoxy, isobutoxy), —OCH₂-cyclopropyl,        —OCH₂-cyclobutyl or —OCH₂-cyclopentyl);    -   1.59 Formula I or any of 1.1-1.56, wherein R_(b), R_(c) and        R_(e) are all H; R_(a) is halo (e.g., chloro or fluoro); and        R_(d) is H;    -   1.60 Formula I or any of 1.1-1.56, wherein R_(b), R_(c) and        R_(e) are all H; and R_(a) and R_(d) are both halo (e.g., chloro        or fluoro);    -   1.61 Formula I or any of 1.1-1.56, wherein R_(b), R_(c) and        R_(e) are all H; R_(a) and R_(d) are both chloro;    -   1.62 Formula I or any of 1.1-1.56, wherein R_(b), R_(c) and        R_(e) are all H; R_(a) is halo (e.g., chloro or fluoro); and        R_(d) is —O—C₁₋₆alkyl (e.g., propoxy, butoxy (e.g., n-butoxy,        isobutoxy), —OCH₂-cyclopropyl, —OCH₂-cyclobutyl or        —OCH₂-cyclopentyl);    -   1.63 Formula I or any of 1.1-1.56, wherein R_(b), R_(c) and        R_(e) are all H; R_(a) is halo (e.g., chloro or fluoro); and        R_(d) is —O—C₃₋₆alkyl (e.g., propoxy, butoxy (e.g., n-butoxy,        isobutoxy), —OCH₂-cyclopropyl, —OCH₂-cyclobutyl or        —OCH₂-cyclopentyl);    -   1.64 Formula I or any of 1.1-1.56, wherein R_(b), R_(c) and        R_(e) are all H; R_(a) is chloro; and R_(d) is butoxy (e.g.,        n-butoxy, isobutoxy);    -   1.65 Formula I or any of 1.1-1.56, wherein R_(b), R_(c) and        R_(e) are all H; R_(a) is chloro; and R_(d) is n-butoxy;    -   1.66 Formula I or any of 1.1-1.56, wherein R_(b), R_(c) and        R_(e) are all H; R_(a) is halo (e.g., chloro or fluoro); and        R_(d) is —O—C₁₋₆alkyl (e.g., propoxy, butoxy (e.g., n-butoxy,        isobutoxy), —OCH₂-cyclopropyl, —OCH₂-cyclobutyl or        —OCH₂-cyclopentyl);    -   1.67 Formula I or any of 1.1-1.56, wherein R_(a), R_(b), R_(c)        and R_(e) are all H and R_(d) is —O—C₁₋₆alkyl;    -   1.68 any of the preceding formulae, wherein the compound is        Formula I(i):

-   -   1.69 any of the preceding formulae, wherein the compound is        Formula (ii):

-   -   1.70 any of the preceding formulae, wherein the compound is        Formula I(iii):

-   -   1.71 any of the preceding formulae, wherein the compound is        selected from a group consisting of:

-   1-(5-Butoxy-2-fluorophenyl)-8-(4-fluorophenoxy)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(5-Butoxy-2-fluorophenyl)-8-(dimethylamino)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(5-Butoxy-2-fluorophenyl)-3-methyl-8-(pyrrolidin-1-yl)-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(5-Butoxy-2-fluorophenyl)-3-methyl-8-(1H-pyrazol-1-yl)-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(5-Butoxy-2-fluorophenyl)-3-methyl-8-(pyridin-2-ylamino)-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(5-Butoxy-2-fluorophenyl)-8-(ethylthio)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(5-Butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carbonitrile;

-   1-(5-Butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxylic    acid;

-   Ethyl    1-(5-butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxylate;

-   1-(5-Butoxy-2-fluorophenyl)-N-ethyl-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxamide;

-   1-(5-Butoxy-2-fluorophenyl)-3-methyl-4-oxo-3a,4-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxamide;

-   8-Chloro-1-(2-chloro-5-(cyclopropylmethoxy)phenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(2,5-Dichlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(2-Chlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(2-Chlorophenyl)-3,5-dimethyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(2,5-Dichlorophenyl)-3,5-dimethyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(5-Butoxy-2-chlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(5-Butoxy-2-fluorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   8-Chloro-1-(2,5-dichlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(5-Butoxy-2-chlorophenyl)-8-chloro-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;

-   1-(5-Butoxy-2-chlorophenyl)-8-methoxy-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;    and

-   1-(2-Chloro-5-(cyclobutylmethoxy)phenyl)-8-methoxy-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;    -   1.72 any of the preceding formulae wherein the compounds inhibit        phosphodiesterase-mediated (e.g., PDE2-mediated) hydrolysis of        cGMP, e.g., with an IC₅₀ of less than 2 μM, more preferably less        than or equal to 250 nM, more preferably less than or equal to        10 nM in a PDE assay, for example, as described in Example 23,        in free or salt form.

In a particular embodiment, the disclosure provides a compound ofFormula I(i):

wherein

-   -   (i) R₁ is C₁₋₄alkyl (e.g., methyl);    -   (ii) R₂ is C₁₋₄alkoxy (e.g., methoxy or ethoxy);    -   (iii) R₃ is H;    -   (iv) R_(b), R_(c) and R_(e) are H; R_(a) is halo and R_(d) is        —O—C₁₋₆alkyl (e.g., propoxy, butoxy (e.g., n-butoxy, isobutoxy),        —OCH₂-cyclopropyl, —OCH₂-cyclobutyl or —OCH₂-cyclopentyl);        in free or salt form.

In a particular embodiment, the disclosure provides a compound ofFormula I(i) wherein

-   -   (i) R₁ is C₁₋₄alkyl (e.g., methyl);    -   (ii) R₂ is C₁₋₄alkoxy (e.g., methoxy or ethoxy);    -   (iii) R₃ is H;    -   (iv) R_(b), R_(c) and R_(e) are H; R_(a) is halo and R_(d) is        —OCH₂-cyclobutyl;        in free or salt form.

In a second aspect, the disclosure provides a pharmaceutical compositioncomprising a Compound of the Disclosure, i.e., Compounds of Formula I,I(i), I(ii) or I(iii), or any of formulae 1.1-1.72, in free orpharmaceutically acceptable salt form, in combination or associationwith a pharmaceutically acceptable diluents or carrier.

The disclosure also provides methods of using the Compounds of theDisclosure for treatment of PDE2-mediated disorders, e.g., disorders asset forth below (especially treatment of anxiety, depression, autismspectrum disorder (ASD), schizophrenia, cognitive impairment). This listis not intended to be exhaustive and may include other diseases anddisorders as set forth below.

Therefore, in a third aspect, the disclosure provides a method for thetreatment of a PDE2-mediated disorder, comprising administering to asubject in need thereof a therapeutically effective amount of a Compoundof the Disclosure disclosed herein, i.e., Compounds of Formula I, I(i),I(ii) or I(iii), or any of formulae 1.1-1.72, in free orpharmaceutically acceptable salt form, or a pharmaceutical compositiondisclosed herein.

In a further embodiment of the third aspect, the disclosure provides amethod for the treatment of the following disorders:

-   -   neurological disorders (such as migraine; epilepsy; Alzheimer's        disease; Parkinson's disease; brain injury; stroke;        cerebrovascular diseases (including cerebral arteriosclerosis,        cerebral amyloid angiopathy, hereditary cerebral hemorrhage, and        brain hypoxia-ischemia); spinal muscular atrophy; lateral        sclerosis; multiple sclerosis;    -   cognitive disorders (including amnesia, senile dementia, HIV        associated dementia, Alzheimer's associated dementia,        Huntington's associated dementia, Lewy body dementia, vascular        dementia, drug related dementia, delirium, and mild cognitive        impairment); and cognitive dysfunction associated with        Parkinson's disease and depression;    -   mental deficiency (including Down syndrome and fragile X        syndrome);    -   sleep disorders (including hypersomnia, circadian rhythm sleep        disorder, insomnia, parasomnia, and sleep deprivation);    -   psychiatric disorders (such as anxiety (including acute stress        disorder, generalized anxiety disorder, social anxiety disorder,        panic disorder, post-traumatic stress disorder (PTSD),        obsessive-compulsive disorder, specific phobia, social phobia,        chronic anxiety disorder and obsessive compulsive disorder);    -   factitious disorder (including acute hallucinatory mania);    -   impulse control disorders (including pathological gambling,        pathological fire-setting, pathological stealing and        intermittent explosive disorder);    -   mood disorders (including bipolar I disorder, bipolar II        disorder, mania, mixed affective state, major depression,        chronic depression, seasonal depression, psychotic depression        and postpartum depression);    -   psychomotor disorders (extrapyraamidal and movement disorders,        e.g., Parkinsonism, Lewy body disease, tremor, drug-induced        tremor, drug-induced tardive dyskineisa, L-dopa-induced        dyskinesia and restless leg syndrome);    -   psychotic disorders (including schizophrenia (e.g., continuous        or episodic, paranoid, hebephrenic, catatonic, undifferentiated        and residual schizophrenic disorders), schizoaffective disorder,        schizophreniform, and delusional disorder);    -   drug dependence (including narcotic dependence, alcoholism,        amphetamine dependence, cocaine addiction, nicotine dependence,        and drug withdrawal syndrome);    -   eating disorders (including anorexia, bulimia, binge eating        disorder, hyperphagia, and pagophagia);    -   pediatric psychiatric disorders (including attention deficit        disorder, attention deficit/hyperactive disorder, conduct        disorder (e.g., tic disorders such as transient, chronic, motor        or vocal tic disorders), autism and autism spectrum disorder        (ASD));    -   mental and behavioral disorders due to psychoactive substance        use;    -   cardiovascular disorder (e.g., pulmonary hypertension and        pulmonary arterial hypertension); and    -   pain (e.g., bone and joint pain (osteoarthritis), repetitive        motion pain, dental pain, cancer pain, myofascial pain (muscular        injury, fibromyalgia), perioperative pain (general surgery,        gynecological), chronic pain and neuropathic pain),        in a subject, preferably a mammal, preferably a human,        comprising administering to said subject a therapeutically        effective amount of a Compound of the Disclosure disclosed        herein, i.e., Compounds of Formula I, I(i), I(ii) or I(iii), or        any of formulae 1.1-1.72, in free or pharmaceutically acceptable        salt form, or a pharmaceutical composition disclosed herein.

In one embodiment, the disease or disorder is selected from a groupconsisting of anxiety, depression, autism spectrum disorder andschizophrenia, for example anxiety and/or depression in autistic and/orschizophrenic patients. In another embodiment, the disease or disorderis cognitive impairment associated with schizophrenia or dementia.

In the fourth aspect, the disclosure provides a Compound of theDisclosure disclosed herein, i.e., Compounds of Formula I, I(i), I(ii)or I(iii), or any of formulae 1.1-1.72, in free or pharmaceuticallyacceptable salt form (for use in the manufacture of a medicament) forthe treatment of a PDE2-mediated disorder as disclosed herein.

In the fifth aspect, the disclosure provides a pharmaceuticalcomposition comprising a Compound of the Disclosure disclosed herein,i.e., Compounds of Formula I, I(i), I(ii) or I(iii), or any of formulae1.1-1.72, in free or pharmaceutically acceptable salt form, incombination or association with a pharmaceutically acceptable diluentsor carrier, for use in the treatment of a PDE2-mediated disorder asdisclosed herein.

DETAILED DESCRIPTION OF THE INVENTION

If not otherwise specified or clear from context, the following termsherein have the following meanings:

-   -   (a) “Alkyl” as used herein is a saturated or unsaturated        hydrocarbon moiety, preferably saturated, preferably having one        to six carbon atoms, preferably having one to four carbon atoms,        which may be linear or branched, and may be optionally mono-,        di- or tri-substituted, e.g., with halogen (e.g., chloro or        fluoro), hydroxy, or carboxy.    -   (b) “Aryl” as used herein is a mono or bicyclic aromatic        hydrocarbon, preferably phenyl, optionally substituted, e.g.,        with alkyl (e.g., methyl), halogen (e.g., chloro or fluoro),        haloalkyl (e.g., trifluoromethyl) or hydroxy.    -   (c) “Heteroaryl” as used herein is an aromatic moiety wherein        one or more of the atoms making up the aromatic ring is sulfur        or nitrogen rather than carbon, e.g., pyridyl or thiadiazolyl,        which may be optionally substituted, e.g., with alkyl, halogen,        haloalkyl or hydroxy.

Compounds of the Disclosure, e.g., Compounds of Formula I, I(i), I(ii)or I(iii), e.g., any of formulae 1.1-1.72, may exist in free or saltform, e.g., as acid addition salts. In this specification unlessotherwise indicated, language such as “Compounds of the Disclosure” isto be understood as embracing the compounds in any form, for examplefree or acid addition salt form, or where the compounds contain acidicsubstituents, in base addition salt form. The Compounds of theDisclosure are intended for use as pharmaceuticals, thereforepharmaceutically acceptable salts are preferred. Salts which areunsuitable for pharmaceutical uses may be useful, for example, for theisolation or purification of free Compounds of the Disclosure or theirpharmaceutically acceptable salts, are therefore also included.Compounds of the Disclosure may in some cases also exist in prodrugform. A prodrug form is compound which converts in the body to aCompound of the Disclosure. For example when the Compounds of theDisclosure contain hydroxy or carboxy substituents, these substituentsmay form physiologically hydrolysable and acceptable esters. As usedherein, “physiologically hydrolysable and acceptable ester” means estersof Compounds of the Disclosure which are hydrolysable underphysiological conditions to yield acids (in the case of Compounds of theDisclosure which have hydroxy substituents) or alcohols (in the case ofCompounds of the Disclosure which have carboxy substituents) which arethemselves physiologically tolerable at doses to be administered.Therefore, wherein the Compound of the Disclosure contains a hydroxygroup, for example, Compound-OH, the acyl ester prodrug of suchcompound, i.e., Compound-O—C(O)—C₁₋₄alkyl, can hydrolyze in the body toform physiologically hydrolysable alcohol (Compound-OH) on the one handand acid on the other (e.g., HOC(O)—C₁₋₄alkyl). Alternatively, whereinthe Compound of the Disclosure contains a carboxylic acid, for example,Compound-C(O)OH, the acid ester prodrug of such compound,Compound-C(O)O—C₁₋₄alkyl can hydrolyze to form Compound-C(O)OH andHO—C₁₋₄alkyl. As will be appreciated, the term thus embracesconventional pharmaceutical prodrug forms.

The Compounds of the Disclosure herein include their enantiomers,diastereoisomers and racemates, as well as their polymorphs, hydrates,solvates and complexes. Some individual compounds within the scope ofthis invention may contain double bonds. Representations of double bondsin this invention are meant to include both the E and the Z isomer ofthe double bond. In addition, some compounds within the scope of thisinvention may contain one or more asymmetric centers. This inventionincludes the use of any of the optically pure stereoisomers as well asany combination of stereoisomers.

It is also intended that the Compounds of the Disclosure encompass theirstable and unstable isotopes. Stable isotopes are nonradioactiveisotopes which contain one additional neutron compared to the abundantnuclides of the same species (i.e., element). It is expected that theactivity of compounds comprising such isotopes would be retained, andsuch compound would also have utility for measuring pharmacokinetics ofthe non-isotopic analogs. For example, the hydrogen atom at a certainposition on the Compounds of the Disclosure may be replaced withdeuterium (a stable isotope which is non-radioactive). Examples of knownstable isotopes include, but not limited to, deuterium, ¹³C, ¹⁵N, ¹⁸O.Alternatively, unstable isotopes, which are radioactive isotopes whichcontain additional neutrons compared to the abundant nuclides of thesame species (i.e., element), e.g., ¹²³I, ¹³¹I, ¹²⁵I, ¹¹C, ¹⁸F, mayreplace the corresponding abundant species of I, C and F. Anotherexample of useful isotope of the compound of the invention is the ¹¹Cisotope. These radio isotopes are useful for radio-imaging and/orpharmacokinetic studies of the compounds of the invention.Isotopically-labeled compounds of Formula I may generally be prepared bycarrying out by substituting an isotopically-labeled reagent for anon-isotopically-labeled reagent.

The phrase “Compounds of the Disclosure” or “PDE 2 inhibitors of theDisclosure” encompasses any and all of the compounds disclosed herewith,e.g., a Compound of Formula I, I(i), I(ii), I(iii) or any of 1.1-1.72 ashereinbefore described, in free or salt form.

The words “treatment” and “treating” are to be understood accordingly asembracing treatment or amelioration of symptoms of the disease as wellas treatment of the cause of the disease. In one embodiment, theinvention provides a method for the treatment of the disease or disorderdisclosed herein. In another embodiment, the invention provides a methodfor the prophylaxis of a disease or disorder as disclosed herein.

For methods of treatment, the word “effective amount” is intended toencompass a therapeutically effective amount to treat a specific diseaseor disorder.

The term “pulmonary hypertension” is intended to encompass pulmonaryarterial hypertension.

The term “subject” includes human or non-human (i.e., animal). Inparticular embodiment, the invention encompasses both human andnonhuman. In another embodiment, the invention encompasses nonhuman. Inother embodiment, the term encompasses human.

The term “comprising” as used in this disclosure is intended to beopen-ended and does not exclude additional, unrecited elements or methodsteps.

The term “cognitive disorders” refers to any disorder comprising asymptom of cognitive deficiency (i.e., subnormal or suboptimalfunctioning in one or more cognitive aspects such as memory, intellect,learning, logic, attention or executive function (working memory) in anindividual compared to other individuals within the same general agepopulation). Therefore, cognitive disorders include but are not limitedto amnesia, senile dementia, HIV associated dementia, Alzheimer'sassociated dementia, Huntington's associated dementia, Lewy bodydementia, vascular dementia, drug related dementia, delirium, and mildcognitive impairment. Cognitive disorders can also be a disorderprimarily but not exclusively related to psychosis (schizophrenia), mooddisorders, bipolar disorders, stroke, frontotemporal dementia,progressive supranuclear palsy, cerebral trauma and drug abuse,Asperger's syndrome and age-associated memory impairment.

Compounds of the Disclosure, e.g., Compounds of Formula I, I(i), I(ii)or I(iii), e.g., any of formulae 1.1-1.72, as hereinbefore described, infree or pharmaceutically acceptable salt form may be used as a soletherapeutic agent, but may also be used in combination or forco-administration with other active agents.

Dosages employed in practicing the present invention will of course varydepending, e.g. on the particular disease or condition to be treated,the particular Compound of the Disclosure used, the mode ofadministration, and the therapy desired. Compounds of the Disclosure maybe administered by any suitable route, including orally, parenterally,transdermally, or by inhalation, but are preferably administered orally.In general, satisfactory results, e.g. for the treatment of diseases ashereinbefore set forth are indicated to be obtained on oraladministration at dosages of the order from about 0.01 to 2.0 mg/kg. Inlarger mammals, for example humans, an indicated daily dosage for oraladministration will accordingly be in the range of from about 0.75 to150 mg, conveniently administered once, or in divided doses 2 to 4times, daily or in sustained release form. Unit dosage forms for oraladministration thus for example may comprise from about 0.2 to 75 or 150mg, e.g. from about 0.2 or 2.0 to 50, 75 or 100 mg of a Compound of theDisclosure, together with a pharmaceutically acceptable diluent orcarrier therefor.

Pharmaceutical compositions comprising Compounds of the Disclosure maybe prepared using conventional diluents or excipients and techniquesknown in the galenic art. The pharmaceutically acceptable carrier maycomprise any conventional pharmaceutical carrier or excipient. Suitablepharmaceutical carriers include inert diluents or fillers, water andvarious organic solvents (such as hydrates and solvates). Thepharmaceutical compositions may, if desired, contain additionalingredients such as flavorings, binders, excipients and the like. Thusfor oral administration, tablets containing various excipients, such ascitric acid, may be employed together with various disintegrants such asstarch, alginic acid and certain complex silicates and with bindingagents such as sucrose, gelatin and acacia. Additionally, lubricatingagents such as magnesium stearate, sodium lauryl sulfate and talc areoften useful for tableting purposes. Solid compositions of a similartype may also be employed in soft and hard filled gelatin capsules.Non-limiting examples of materials, therefore, include lactose or milksugar and high molecular weight polyethylene glycols. When aqueoussuspensions or elixirs are desired for oral administration the activecompound therein may be combined with various sweetening or flavoringagents, coloring matters or dyes and, if desired, emulsifying agents orsuspending agents, together with diluents such as water, ethanol,propylene glycol, glycerin, or combinations thereof. The pharmaceuticalcomposition may, for example, be in a form suitable for oraladministration as a tablet, capsule, pill, powder, sustained releaseformulation, solution or suspension, for parenteral injection as asterile solution, suspension or emulsion, for topical administration asan ointment or cream or for rectal administration as a suppository.

The compounds of the Disclosure herein and their pharmaceuticallyacceptable salts may be made using the methods as described andexemplified herein and by methods similar thereto and by methods knownin the chemical art. Such methods include, but not limited to, thosedescribed below. If not commercially available, starting materials forthese processes may be made by procedures, which are selected from thechemical art using techniques which are similar or analogous to thesynthesis of known compounds. All references cited herein are herebyincorporated by reference in their entirety.

Example 11-(5-Butoxy-2-fluorophenyl)-8-(4-fluorophenoxy)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

(a) 5-Butoxy-2-fluorobenzenamine

A mixture of 4-fluoro-3-nitrophenol (1) (2.81 g, 17.9 mmol),1-bromobutane (3.43 g, 25.0 mmol) and cesium carbonate (11.6 g, 35.7mmol) in anhydrous DMF (15 mL) is stirred at room temperature for 18 h.After the solvent is removed under reduced pressure, the residue istreated with water (400 mL) and extracted with methylene (3×50 mL). Thecombined organic phase is evaporated to dryness to give4-butoxy-1-fluoro-2-nitrobenzene as an orange oil. To a solution of thecrude 4-butoxy-1-fluoro-2-nitrobenzene in EtOH (10 mL) is slowly addedconcentrated HCl (10 mL). The mixture is stirred at room temperature for5 min, and then tin(II) chloride (8.40 g, 44.3 mmol) is added. Afterstirring at room temperature for 16 h, the reaction mixture is treatedwith water (500 mL) and extracted with methylene (4×50 mL). The combinedorganic phase is washed with brine (40 mL), and then evaporated todryness under reduced pressure. The obtained crude product is furtherpurified with a neutral alumina oxide column using a gradient of 0-100%ethyl acetate in hexane as eluent to give 5-butoxy-2-fluorobenzenaminean oil (2.42 g, 74% yield). MS (ESI) m/z 184.1 [M+H]⁺.

(b) (5-Butoxy-2-fluorophenyl)hydrazine

A solution of sodium nitrite (1.04 g, 15.1 mmol) in water (5 mL) isadded dropwise to a suspension of 5-butoxy-2-fluorobenzenamine (2.30 g,12.6 mmol) in concentrated hydrochloric acid (12 mL) at 0° C. After thecompletion of the addition, the reaction mixture is stirred at 0° C. for30 min, and then a solution of tin (II) chloride dihydrate (6.86 g, 30.4mmol) in concentrated hydrochloric acid (3 mL) is added. The reactionmixture is stirred at room temperature overnight, and then filtered. Thefilter cake is washed with 6 N HCl (3×4 mL) and hexane (3×5 mL)successively, and then dried under vacuum to give 3.18 g of the crudeproduct, which is used directly in the next step without furtherpurification. MS (ESI) m/z 199.1 [M+H]⁺.

(c)8-Bromo/Chloro-1-(5-butoxy-2-fluorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

To a suspension of (4-butoxy-2-fluorophenyl)hydrazine (860 mg, 4.34mmol) and 3-acetyl-6-bromo-4-hydroxy-1,5-naphthyridin-2(1H)-one (500 mg,1.77 mmol) in dioxane (4 mL) is added concentrated HCl (0.1 mL). Thereaction mixture in a sealed tube is stirred at room temperature for 5min and then heated in a microwave reactor at 160° C. for 5 h. Aftercooled to room temperature, the reaction mixture is treated with water(200 mL) and then extracted with CH₂Cl₂/MeOH (10/1) (4×50 mL). Thecombined organic phase is evaporated to dryness. The obtained residue ispurified by silica-gel column chromatography using a gradient of 0-100%ethyl acetate in hexane as eluent to give 580 mg of product, whichcontains 22% of8-chloro-1-(5-butoxy-2-fluorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one(MS (ESI) m/z 401.1 [M+H]⁺) and 68%8-bromo-1-(5-butoxy-2-fluorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one(MS (ESI) m/z 445.1 [M+H]⁺). The two compounds co-eluted on the columnand are used directly in the next step without further separation.

(d)1-(5-Butoxy-2-fluorophenyl)-8-(4-fluorophenoxy)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

A suspension of8-bromo/chloro-1-(5-butoxy-2-fluorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one(41.0 mg), 4-fluorophenol (112 mg, 1.00 mmol) and cesium carbonate (97mg, 0.30 mmol) in dioxane (0.6 mL) in a sealed microwave vial is heatedin a microwave reactor at 160° C. for 5 h. After cooled to roomtemperature, the reaction mixture is treated with water (100 mL) andextracted with CH₂Cl₂ (4×25 mL). The combined organic phase isevaporated to dryness. The obtained residue is purified with asemi-preparative HPLC system using a gradient of 0-70% acetonitrile inwater containing 0.1% formic acid over 16 min to give 17 mg of1-(5-butoxy-2-fluorophenyl)-8-(4-fluorophenoxy)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-oneas an off-white solid. ¹H NMR (500 MHz, Chloroform-d) δ 11.24 (s, 1H),7.81 (d, J=8.9 Hz, 1H), 7.13 (d, J=8.8 Hz, 1H), 6.88 (dd, J=6.0, 3.1 Hz,1H), 6.85-6.78 (m, 4H), 6.76-6.70 (m, 1H), 6.62 (dd, J=9.2, 9.2 Hz, 1H),4.03-3.78 (m, 2H), 2.79 (s, 3H), 1.81-1.74 (m, 2H), 1.58-1.45 (m, 2H),1.00 (t, J=7.4 Hz, 3H). MS (ESI) m/z 477.2 [M+H]⁺.

Example 21-(5-Butoxy-2-fluorophenyl)-8-(dimethylamino)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

The title compound is prepared in an analogous fashion following theprocedure described in the synthesis of Example 1 wherein 40%dimethylamine solution is added in step (d) instead of 4-fluorophenol.¹H NMR (500 MHz, Chloroform-d) δ 10.82 (s, 1H), 7.56 (d, J=9.1 Hz, 1H),7.15-7.08 (m, 2H), 6.99-6.92 (m, 1H), 6.80 (d, J=9.0 Hz, 1H), 3.97 (t,J=6.5 Hz, 2H), 2.81 (s, 3H), 2.77 (s, 6H), 1.81-1.71 (m, 2H), 1.53-1.42(m, 2H), 0.96 (t, J=7.4 Hz, 3H). MS (ESI) m/z 410.2 [M+H]⁺.

Example 31-(5-Butoxy-2-fluorophenyl)-3-methyl-8-(pyrrolidin-1-yl)-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

The title compound is prepared in an analogous fashion following theprocedure described in the synthesis of Example 1 wherein pyrrolidine isadded in step (d) instead of 4-fluorophenol. ¹H NMR (500 MHz,Chloroform-d) δ 10.28 (s, 1H), 7.47 (d, J=9.0 Hz, 1H), 7.15-7.08 (m,2H), 7.00-6.92 (m, 1H), 6.55 (d, J=9.0 Hz, 1H), 3.97 (t, J=6.5 Hz, 2H),3.16-3.01 (m, 4H), 2.80 (s, 3H), 1.95-1.84 (m, 4H), 1.80-1.71 (m, 2H),1.53-1.43 (m, 2H), 0.96 (t, J=7.4, 7.4 Hz, 3H). MS (ESI) m/z 436.2[M+H]⁺.

Example 41-(5-Butoxy-2-fluorophenyl)-3-methyl-8-(1H-pyrazol-1-yl)-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

The title compound is prepared in an analogous fashion following theprocedure described in the synthesis of Example 1 wherein 1H-pyrazole isadded in step (d) instead of 4-fluorophenol. ¹H NMR (500 MHz,Chloroform-d) δ 10.83 (s, 1H), 8.15 (d, J=8.9 Hz, 1H), 7.83 (d, J=8.9Hz, 1H), 7.67 (dd, J=1.7, 0.8 Hz, 1H), 7.59 (dd, J=2.6, 0.8 Hz, 1H),7.25-7.16 (m, 2H), 7.14-7.08 (m, 1H), 6.33 (dd, J=2.6, 1.6 Hz, 1H), 4.00(t, J=6.5 Hz, 2H), 2.84 (s, 3H), 1.82-1.72 (m, 2H), 1.53-1.43 (m, 2H),0.96 (t, J=7.4 Hz, 3H). MS (ESI) m/z 433.2 [M+H]⁺.

Example 51-(5-Butoxy-2-fluorophenyl)-3-methyl-8-(pyridin-2-ylamino)-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

A suspension of the crude8-bromo/chloro-1-(5-butoxy-2-fluorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-onesynthesized in step c of Example 1 (41.0 mg), pyridin-2-amine (160 mg,1.7 mmol), Pd₂(dba)₃ (8 mg), Xantphos (10 mg) and cesium carbonate (130mg, 0.40 mmol) in dioxane (0.6 mL) is heated in at 100° C. for 60 h.After cooled to room temperature, the reaction mixture is treated withDMF (5 mL) and then filtered. The filtrate is isolated with asemi-preparative HPLC system using a gradient of 0-30% acetonitrile inwater containing 0.1% formic acid over 16 min to give 11 mg of1-(5-butoxy-2-fluorophenyl)-3-methyl-8-(pyridin-2-ylamino)-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-oneas an off-white solid. ¹H NMR (500 MHz, DMSO-d₆) δ 11.43 (s, 1H), 9.67(s, 1H), 8.16-8.09 (m, 1H), 7.68 (d, J=9.0 Hz, 1H), 7.38-7.32 (m, 1H),7.32-7.27 (m, 2H), 7.19-7.10 (m, 2H), 6.98-6.91 (m, 1H), 6.83-6.76 (m,1H), 3.99 (t, J=6.4 Hz, 2H), 2.60 (s, 3H), 1.71-1.60 (m, 2H), 1.45-1.31(m, 2H), 0.87 (t, J=7.4 Hz, 3H). MS (ESI) m/z 459.2 [M+H]⁺.

Example 61-(5-Butoxy-2-fluorophenyl)-8-(ethylthio)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

The title compound is prepared in an analogous fashion following theprocedure described in the synthesis of Example 1 wherein ethanethiol isadded in step (d) instead of 4-fluorophenol. ¹H NMR (500 MHz,Chloroform-d) δ 11.00 (s, 1H), 7.56 (d, J=8.7 Hz, 1H), 7.24 (d, J=8.7Hz, 1H), 7.18-7.09 (m, 2H), 7.03-6.98 (m, 1H), 3.97 (t, J=6.4 Hz, 2H),2.81 (s, 3H), 2.51 (q, J=7.4 Hz, 2H), 1.81-1.73 (m, 2H), 1.53-1.44 (m,2H), 1.01 (t, J=7.4 Hz, 3H), 0.97 (t, J=7.4 Hz, 3H). MS (ESI) m/z 427.2[M+H]⁺.

Example 71-(5-Butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carbonitrile

A suspension of the crude8-bromo/chloro-1-(5-butoxy-2-fluorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-oneprepared in step c of Example 1 (140 mg) and copper(I) cyanide (50 mg,0.56 mmol) in pyridine (1.5 mL) in a seal microwave vial is heated in amicrowave reactor at 180° C. for 5 h. After cooled to room temperature,the solvent is removed under reduced pressure. The residue is treatedwith ethyl acetate (15 mL), and then filtered. The filtrate is washedwith water three times (3×5 mL), and then evaporated to dryness. Theobtained crude product is purified by silica gel column chromatographyto give 71 mg of1-(5-butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carbonitrileas an off white solid. ¹H NMR (500 MHz, Chloroform-d) δ 11.23 (s, 1H),7.80 (d, J=8.5 Hz, 1H), 7.73 (d, J=8.2 Hz, 1H), 7.23-7.15 (m, 1H),7.13-7.08 (m, 1H), 7.08-7.01 (m, 1H), 4.00 (t, J=6.5 Hz, 2H), 2.82 (s,3H), 1.84-1.74 (m, 2H), 1.53-1.47 (m, 2H), 0.98 (t, J=7.4 Hz, 3H). MS(ESI) m/z 392.1 [M+H]⁺.

Example 81-(5-Butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxylicacid

To a suspension of1-(5-butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carbonitrile(56 mg, 0.14 mmol) in dioxane (1.0 mL) is added concentratedhydrochloric acid (0.15 mL). The reaction mixture is stirred at 100° C.for 24 h. After the solvents are removed under reduced pressure, theresidue is further dried under vacuum to afford1-(5-butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxylicacid (45 mg, 77% yield) as an off white solid. ¹H NMR (500 MHz,Chloroform-d) δ 10.87 (s, 1H), 9.49 (s, 1H), 8.30 (d, J=8.1 Hz, 1H),7.90 (d, J=8.4 Hz, 1H), 7.30-7.23 (m, 1H), 7.19-7.15 (m, 1H), 7.14-7.08(m, 1H), 4.12-3.92 (m, 2H), 2.84 (s, 3H), 1.86-1.74 (m, 2H), 1.53-1.45(m, 2H), 0.98 (t, J=7.4, 7.4 Hz, 3H). MS (ESI) m/z 411.1 [M+H]⁺.

Example 9 Ethyl1-(5-butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxylate

A mixture of1-(5-butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxylicacid (20 mg, 0.049 mmol) and concentrated sulfuric acid (10 μL) inethanol (0.60 mL) in a sealed microwave vial is heated in a microwavereactor at 120° C. for 1 h. After cooled to room temperature, thereaction mixture is concentrated under reduced pressure. The obtainedresidue is purified with a semi-preparative HPLC to give ethyl1-(5-butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxylate(17 mg, 77% yield) as an off white solid. ¹H NMR (500 MHz, Chloroform-d)δ 11.07 (s, 1H), 8.23 (d, J=8.6 Hz, 1H), 7.79 (d, J=8.6 Hz, 1H),7.19-7.13 (m, 2H), 7.07-7.00 (m, 1H), 4.35-4.24 (m, 2H), 3.99 (t, J=6.5Hz, 2H), 2.83 (s, 3H), 1.82-1.72 (m, 2H), 1.56-1.42 (m, 2H), 1.30 (t,J=7.2 Hz, 3H), 0.97 (t, J=7.4 Hz, 3H). MS (ESI) m/z 439.2 [M+H]⁺.

Example 101-(5-Butoxy-2-fluorophenyl)-N-ethyl-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxamide

(a)1-(5-Butoxy-2-fluorophenyl)-4-chloro-N-ethyl-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxamide

To a solution of1-(5-butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxylicacid (25 mg, 0.061 mmol) in CH₂Cl₂ (0.75 mL) is added thionyl chloride(45 μL, 0.62 mmol), followed by two drops of DMF. After stirring at 46°C. overnight, the reaction mixture is evaporated to dryness underreduced pressure. The residue is dissolved in CH₂Cl₂ (0.80 mL), and thenethanamine is bubbled through the solution at room temperature for 30min. After the solvent is removed under reduced pressure, the residue iswashed with water twice times (2×1 mL), and then dried under vacuum togive 26 mg of crude1-(5-butoxy-2-fluorophenyl)-4-chloro-N-ethyl-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxamide,which is used in the next step without further purification. MS (ESI)m/z 456.2 [M+H]⁺.

(b)1-(5-Butoxy-2-fluorophenyl)-N-ethyl-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxamide

A suspension of1-(5-butoxy-2-fluorophenyl)-4-chloro-N-ethyl-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxamide(26 mg, 0.057 mmol) and concentrated hydrochloric acid (10 μL) indioxane (0.50 mL) in a sealed vial is heated in a microwave reactor at130° C. for 1 h. After cooled to room temperature, the mixture isevaporated to dryness under reduced pressure. The obtained crude productis purified with a semi-preparative HPLC to give1-(5-butoxy-2-fluorophenyl)-N-ethyl-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxamide(11 mg, 44% yield) as a pale yellow solid. ¹H NMR (500 MHz,Chloroform-d) δ 10.77 (s, 1H), 8.30 (d, J=8.5 Hz, 1H), 7.81 (d, J=8.6Hz, 1H), 7.26-7.16 (m, 2H), 7.13-7.06 (m, 1H), 6.84-6.76 (m, 1H),4.10-3.90 (m, 2H), 3.42-3.24 (m, 2H), 2.83 (s, 3H), 1.87-1.72 (m, 2H),1.55-1.42 (m, 2H), 1.11 (t, J=7.3 Hz, 3H), 0.97 (t, J=7.4 Hz, 3H). MS(ESI) m/z 438.2 [M+H]⁺.

Example 111-(5-Butoxy-2-fluorophenyl)-3-methyl-4-oxo-3a,4-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxamide

To a suspension of1-(5-butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carbonitrile(10 mg, 0.026 mmol) in dioxane (0.2 mL) is added 6N NaOH aqueoussolution (40 μL). The reaction mixture is heated at 100° C. for 2 h.After cooled to room temperature, the reaction mixture is evaporated todryness under reduced pressure. The residue is purified with asemi-preparative HPLC system to give1-(5-butoxy-2-fluorophenyl)-3-methyl-4-oxo-3a,4-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxamide(3.2 mg, 30% yield) as an off white solid. ¹H NMR (500 MHz,Chloroform-d) δ 10.13 (s, 1H), 8.29 (d, J=8.4 Hz, 1H), 7.76 (d, J=8.3Hz, 1H), 7.25-7.14 (m, 2H), 7.10-7.02 (m, 1H), 6.59 (s, 1H), 5.32 (s,1H), 3.99 (t, J=6.5 Hz, 2H), 2.81 (s, 3H), 1.82-1.74 (m, 2H), 1.52-1.46(m, 2H), 0.97 (t, J=7.4, 7.4 Hz, 3H). MS (ESI) m/z 410.2 [M+H]⁺.

Example 128-Chloro-1-(2-chloro-5-(cyclopropylmethoxy)phenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

(a) 5-(Benzyloxy)-2-chlorobenzenamine

A mixture of 4-chloro-5-nitrophenol (2.25 g, 13.0 mmol),(bromomethyl)benzene (2.33 g, 13.6 mmol) and cesium carbonate (8.50 g,25.9 mmol) in anhydrous N,N-Dimethylacetamide (10 mL) is stirred at roomtemperature for 2 h. After the solvent is removed under reducedpressure, the residue is treated with water (300 mL) and then extractedwith methylene three times (3×30 mL). The combined organic phase isevaporated to dryness to give 4-(benzyloxy)-1-chloro-2-nitrobenzene asan oil. To a solution of the crude 4-(benzyloxy)-1-chloro-2-nitrobenzenein EtOH (10 mL) is slowly added concentrated HCl (8 mL). The mixture isstirred at room temperature for 5 min, and then tin(II) chloride (8.0 g,42.0 mmol) is added. After stirring at room temperature for 0.5 h, thereaction mixture is treated with water (400 mL) and then extracted withmethylene (4×30 mL). The combined organic phase is washed with saturatedNaHCO₃ (30 mL) and brine (30 mL) successively, and then evaporated todryness to give 3.0 g of 5-(benzyloxy)-2-chlorobenzenamine as lightorange solid. MS (ESI) m/z 234.1 [M+H]⁺.

(b) (5-(Benzyloxy)-2-chlorophenyl)hydrazine

A solution of sodium nitrite (226 mg, 3.28 mmol) in water (3 mL) isadded dropwise to a suspension of 5-(benzyloxy)-2-chlorobenzenamine (640mg, 2.74 mmol) in concentrated hydrochloric acid (5 mL) at 0° C. Afterthe completion of the addition, the reaction mixture is stirred at 0° C.for 30 min. A solution of tin (II) chloride (2.08 g, 11.0 mmol) inconcentrated hydrochloric acid (3 mL) is added. The resulting suspensionis stirred at room temperature for 2 h, and then filtered. The filtercake is collected. The filtrate is basified to pH 10 with 10 N NaOH, andthen extracted with CH₂Cl₂ (3×40 mL). The combined organic phase isevaporated to dryness. The obtained residue and the collected filtercake are combined and purified with a neutral aluminum oxide columnusing a gradient of 0-20% methanol in ethyl acetate to give(5-(benzyloxy)-2-chlorophenyl)hydrazine (300 mg, 44% yield). MS (ESI)m/z 249.1 [M+H]⁺.

(c)8-Chloro-1-(2-chloro-5-hydroxyphenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

To a suspension of (5-(benzyloxy)-2-fluorophenyl)hydrazine (650 mg, 2.6mmol) and 3-acetyl-6-bromo-4-hydroxy-1,5-naphthyridin-2(1H)-one (200 mg,0.71 mmol) in dioxane (2 mL) is added concentrated HCl (0.1 mL). Thereaction mixture in a sealed tube is stirred at room temperature for 5min and then heated at 110° C. for 2 days. After cooling to roomtemperature, the reaction mixture us treated with water (200 mL) andthen extracted with CH₂Cl₂/MeOH (10/1) (4×50 mL). The combined organicphase is evaporated to dryness to give 409 mg of crude8-chloro-1-(2-chloro-5-hydroxyphenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one,which is used directly in next step without further purification. Asmall amount of the crude product is purified with a semi-preparativeHPLC for structural verification. ¹H NMR (500 MHz, DMSO-d₆) δ 11.70 (s,1H), 10.13 (s, 1H), 7.77 (d, J=8.7 Hz, 1H), 7.54 (d, J=8.7 Hz, 1H),7.47-7.41 (m, 1H), 7.02-6.95 (m, 2H), 2.60 (s, 3H). MS (ESI) m/z 361.0[M+H]⁺.

(d)8-Chloro-1-(2-chloro-5-(cyclopropylmethoxy)phenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

A suspension of8-chloro-1-(2-chloro-5-hydroxyphenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one(60 mg, 0.17 mmol), (bromomethyl)cyclopropane (30 μL, 0.27 mmol) andsodium carbonate (36 mg, 0.23 mmol) in DMF (1.2 mL) in a sealed reactionvial is heated at 100° C. for 2 days. After cooled to room temperature,the reaction mixture is filtered. The filtrate is separated with asemi-preparative HPLC system using a gradient of 0-63% acetonitrile inwater containing 0.1% formic acid over 16 min to give8-chloro-1-(2-chloro-5-(cyclopropylmethoxy)phenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-oneas an off-white solid (7 mg, 10% yield). ¹H NMR (500 MHz, Chloroform-d)δ 11.08 (s, 1H), 7.71 (d, J=8.6 Hz, 1H), 7.46 (d, J=8.6 Hz, 1H), 7.38(d, J=8.6 Hz, 1H), 7.14-7.06 (m, 2H), 3.86 (dd, J=7.0, 2.8 Hz, 2H), 2.83(s, 3H), 1.37-1.24 (m, 1H), 0.73-0.62 (m, 2H), 0.44-0.29 (m, 2H). MS(ESI) m/z 415.1 [M+H]⁺.

Example 131-(2,5-Dichlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

To a suspension of 2,5-dichlorophenylhydrazine (80 mg, 0.45 mmol) and3-acetyl-4-hydroxy-1,5-naphthyridin-2(1H)-one (62 mg, 0.30 mmol) inethanol (2 mL) is added concentrated HCl (0.1 mL). The reaction mixturein a sealed tube is heated in a microwave reactor at 160° C. for 5 h.After cooled to room temperature, the reaction mixture is diluted withDMF (10 mL) and then filtered. The filtrate is isolated with asemi-preparative HPLC system to give1-(2,5-Dichlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one(20 mg, 50% yield). ¹H NMR (500 MHz, Chloroform-d) δ 9.95 (s, 1H), 8.27(dd, J=4.5, 1.4 Hz, 1H), 7.66-7.56 (m, 2H), 7.52-7.43 (m, 2H), 7.37 (dd,J=8.3, 4.5 Hz, 1H), 2.81 (s, 3H). MS (ESI) m/z 345.0 [M+H]⁺.

Example 141-(2-Chlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

The title compound is prepared in an analogous fashion following theprocedure described in the synthesis of Example 13 wherein(2-chlorophenyl)hydrazine is added instead of2,5-dichlorophenylhydrazine. ¹H NMR (500 MHz, Chloroform-d) δ 10.22 (s,1H), 8.24 (dd, J=4.5, 1.4 Hz, 1H), 7.64 (dd, J=8.3, 1.4 Hz, 1H),7.61-7.53 (m, 2H), 7.52-7.42 (m, 2H), 7.34 (dd, J=8.3, 4.5 Hz, 1H), 2.82(s, 3H). MS (ESI) m/z 311.1 [M+H]⁺.

Example 151-(2-Chlorophenyl)-3,5-dimethyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

To a stirred suspension of sodium hydride (24 mg, 0.10 mmol) in DMF(0.60 mL) is added1-(2-chlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one(12 mg, 0.039 mmol). After the suspension is stirred at room temperaturefor 0.5 h, methyl iodide (274 mg, 1.93 mmol) is added. The mixture isstirred at room temperature for 1 h, and then cooled to −70° C. Water (1mL) is added to quench the reaction, followed by adding DMF (5 mL). Theresulting mixture is filtered and the filtrate is isolated with asemi-preparative HPLC system to afford1-(2-Chlorophenyl)-3,5-dimethyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one(12 mg, 72% yield). ¹H NMR (500 MHz, Chloroform-d) δ 8.22 (dd, J=4.6,1.2 Hz, 1H), 7.67 (dd, J=8.6, 1.0 Hz, 1H), 7.59-7.53 (m, 2H), 7.51-7.41(m, 2H), 7.38 (dd, J=8.6, 4.2 Hz, 1H), 3.73 (s, 3H), 2.80 (s, 3H). MS(ESI) m/z 325.1 [M+H]⁺.

Example 161-(2,5-Dichlorophenyl)-3,5-dimethyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

The title compound is prepared in an analogous fashion following theprocedure described in the synthesis of Example 15 wherein1-(2,5-dichlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-oneis added instead of1-(2-chlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one.¹H NMR (500 MHz, Chloroform-d) δ 8.27 (dd, J=4.5, 1.4 Hz, 1H), 7.71 (dd,J=8.7, 1.2 Hz, 1H), 7.60 (d, J=2.2 Hz, 1H), 7.53-7.46 (m, 2H), 7.44 (dd,J=8.6, 4.4 Hz, 1H), 3.76 (s, 3H), 2.81 (s, 3H). MS (ESI) m/z 359.0[M+H]⁺.

Example 171-(5-Butoxy-2-chlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

The title compound is prepared in an analogous fashion following theprocedure described in the synthesis of Example 13 wherein(5-butoxy-2-chlorophenyl)hydrazine is added instead of2,5-dichlorophenylhydrazine. MS (ESI) m/z 383.2 [M+H]⁺.

Example 181-(5-Butoxy-2-fluorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

The title compound is prepared in an analogous fashion following theprocedure described in the synthesis of Example 13 wherein(5-butoxy-2-fluorophenyl)hydrazine is added instead of2,5-dichlorophenylhydrazine. ¹H NMR (500 MHz, Chloroform-d) δ 10.69 (s,1H), 8.32 (dd, J=4.6, 1.4 Hz, 1H), 7.69 (dd, J=8.4, 1.5 Hz, 1H), 7.37(dd, J=8.3, 4.5 Hz, 1H), 7.21-7.07 (m, 2H), 7.04-6.96 (m, 1H), 3.98 (t,J=6.5 Hz, 2H), 2.82 (s, 3H), 1.84-1.68 (m, 2H), 1.56-1.42 (m, 2H), 0.97(t, J=7.4 Hz, 3H). MS (ESI) m/z 367.2 [M+H]⁺.

Example 198-Chloro-1-(2,5-dichlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

The title compound is prepared in an analogous fashion following theprocedure described in the synthesis of Example 13 wherein3-acetyl-6-bromo-4-hydroxy-1,5-naphthyridin-2(1H)-one is added insteadof 3-acetyl-4-hydroxy-1,5-naphthyridin-2(1H)-one. ¹H NMR (500 MHz,Chloroform-d) δ 10.94 (s, 1H), 7.67 (d, J=8.6 Hz, 1H), 7.58 (d, J=2.3Hz, 1H), 7.55-7.46 (m, 2H), 7.38 (d, J=8.5 Hz, 1H), 2.81 (s, 3H). MS(ESI) m/z 379.0 [M+H]⁺.

Example 201-(5-Butoxy-2-chlorophenyl)-8-chloro-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

The title compound is prepared in an analogous fashion following theprocedure described in the synthesis of Example 13 wherein(5-butoxy-2-chlorophenyl)hydrazine and3-acetyl-6-bromo-4-hydroxy-1,5-naphthyridin-2(1H)-one are added insteadof 2,5-dichlorophenylhydrazine and3-acetyl-4-hydroxy-1,5-naphthyridin-2(1H)-one. ¹H NMR (500 MHz,Chloroform-d) δ 10.83 (s, 1H), 7.66 (d, J=8.6 Hz, 1H), 7.43 (d, J=8.9Hz, 1H), 7.36 (d, J=8.5 Hz, 1H), 7.09 (d, J=2.9 Hz, 1H), 7.04 (dd,J=8.9, 2.9 Hz, 1H), 3.99 (dt, J=14.3, 7.0 Hz, 2H), 2.81 (s, 3H),1.91-1.71 (m, 2H), 1.56-1.40 (m, 2H), 0.97 (t, J=7.4 Hz, 3H). MS (ESI)m/z 417.1 [M+H]⁺.

Example 211-(5-Butoxy-2-chlorophenyl)-8-methoxy-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

To a solution of1-(5-butoxy-2-chlorophenyl)-8-chloro-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one(50 mg, 0.12 mmol) in dioxane (2.0 mL) is added sodium methoxidesolution (0.5 N, 1 mL in MeOH), followed by adding NaH (60 mg, 2.5 mmol)in portions under argon. The mixture is stirred at room temperature for10 min and then heated in a sealed tube in a microwave reactor at 160°C. for 6 h. After the reaction mixture is cooled to room temperature,additional sodium methoxide solution (0.5 N, 0.8 mL in MeOH) and NaH (80mg, 3.3 mmol) are added. The reaction vial is sealed and heated in amicrowave reactor at 160° C. for another 6 h. The mixture is cooled toroom temperature, quenched with water (100 mL), and then extracted withCH₂Cl₂ (4×25 mL). The combined organic phase is evaporated to drynessunder reduced pressure. The obtained residue is purified with asemi-preparative HPLC system using a gradient of 0-70% acetonitrile inwater containing 0.1% formic acid over 16 min to give1-(5-butoxy-2-chlorophenyl)-8-methoxy-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-oneas an off-white solid (36 mg, 72% yield). ¹H NMR (500 MHz, Chloroform-d)δ 10.82 (s, 1H), 7.65 (d, J=8.8 Hz, 1H), 7.41 (d, J=8.9 Hz, 1H), 7.12(d, J=2.8 Hz, 1H), 6.98 (dd, J=8.9, 2.8 Hz, 1H), 6.87 (d, J=8.8 Hz, 1H),4.08-3.88 (m, 2H), 3.36 (s, 3H), 2.82 (s, 3H), 1.83-1.69 (m, 2H),1.55-1.39 (m, 2H), 0.96 (t, J=7.4 Hz, 3H). MS (ESI) m/z 413.1 [M+H]⁺.

Example 221-(2-Chloro-5-(cyclobutylmethoxy)phenyl)-8-methoxy-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

(a)8-Chloro-1-(2-chloro-5-(cyclobutylmethoxy)phenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

The title compound is prepared in an analogous fashion following theprocedure described in the synthesis of Example 13 wherein(2-chloro-5-(cyclobutylmethoxy)phenyl)hydrazine and3-acetyl-6-bromo-4-hydroxy-1,5-naphthyridin-2(1H)-one are added insteadof 2,5-dichlorophenylhydrazine and3-acetyl-4-hydroxy-1,5-naphthyridin-2(1H)-one.

(b)1-(2-Chloro-5-(cyclobutylmethoxy)phenyl)-8-methoxy-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one

To a solution of crude8-chloro-1-(2-chloro-5-(cyclobutylmethoxy)-phenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one(50 mg, 0.11 mmol) in methanol (1.5 mL) is added sodium methoxidesolution (5M, 1 mL in MeOH), followed by adding CuI (22 mg, 0.12 mmol)under argon. The mixture is heated in a sealed tube in a microwavereactor at 130° C. for 1.5 h. The reaction mixture is cooled to roomtemperature, quenched with water (20 mL), and then extracted with ethylacetate (20 mL). The combined organic phase is evaporated to drynessunder reduced pressure. The obtained residue is purified with asemi-preparative HPLC system using a gradient of 0-43% acetonitrile inwater containing 0.1% formic acid over 16 min to give1-(2-Chloro-5-(cyclobutylmethoxy)phenyl)-8-methoxy-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-oneas a white solid (14 mg, 30% yield). ¹H NMR (500 MHz, Chloroform-d) δ10.67 (s, 1H), 7.62 (d, J=8.9 Hz, 1H), 7.41 (d, J=8.9 Hz, 1H), 7.13 (d,J=2.9 Hz, 1H), 6.98 (dd, J=8.9, 2.9 Hz, 1H), 6.86 (d, J=8.9 Hz, 1H),3.97-3.90 (m, 2H), 3.36 (s, 3H), 2.82 (s, 3H), 2.79-2.72 (m, 1H),2.16-2.09 (m, 2H), 1.99-1.90 (m, 2H), 1.88-1.81 (m, 2H). MS (ESI) m/z425.1 [M+H]⁺.

Example 23 Measurement of PDE2 Inhibition In Vitro

r-hPDE2A

(Accession No. NM_002599, Homo sapiens phosphodiesterase 2A,cGMP-stimulated, transcript variant 1) A mammalian expression cloningvector with recombinant cDNA copy of the gene is purchased from Origene.Protein is expressed via transient transfection of HEK293 cells. Thecells are harvested at 48 hours after transfection, washed once with TBSbuffer (50 mM Tris-HCl, pH 7.5, 150 mM NaCl), then lysed by sonicationin cold homogenization buffer (50 mM Tris-HCl, pH 7.5, 5 mM MgCl₂, 1×protease inhibitor cocktail). The homogenate is centrifuged for 30 minat 15,000 g at 4° C. to obtain the soluble cytosolic fraction. Theprotein concentration of the cytosol is determined using BCA ProteinAssay Kit (Pierce) with bovine serum albumin as a standard.

Assay:

PDE2A is assayed with FL-cAMP as substrate. An enzyme titration is firstperformed to determine the working concentration of PDE. Theconcentration of the enzyme giving activity of 100 ΔmP in the absence ofinhibitor is deemed an appropriate working concentration for PDE.

PDE enzyme is diluted in a standard reaction buffer (10 mM Tris-HCl pH7.2, 10 mM MgCl₂, 0.1% BSA, 0.05% NaN₃) according to the titrationcurve. For PDE2 assay the reaction buffer is supplemented with 1 μM cGMPto fully activate the enzyme. 99 μl of diluted enzyme solution is addedinto each well in a flat bottom 96-well polystyrene plate and then ˜1 μlof test compound dissolved in 100% DMSO is added. The compounds aremixed and pre-incubated with the enzyme for 10 min at room temperature.

The FL-cNMP conversion reaction is initiated by addition of substrate(45 nM final). Enzyme and inhibitor mix (16 μl) and substrate solution(4 μl of 0.225 μM) are combined in a 384-well microtiter plate. Thereaction is incubated in the dark at room temperature for 15 min. Thereaction is halted by addition of 60 μl of binding reagent (1:400dilution of IMAP beads in binding buffer supplemented with 1:1800dilution of antifoam) to each well of the 384-well plate. The plate isincubated at room temperature for 1 hour to allow IMAP binding toproceed to completion, and then placed in an Envision multimodemicroplate reader (PerkinElmer, Shelton, Conn.) to measure thefluorescence polarization (Amp).

A decrease in cAMP concentration, measured as decreased Amp, isindicative of inhibition of PDE activity. IC₅₀ values are determined bymeasuring enzyme activity in the presence of 8 to 16 concentrations ofcompound ranging from 0.00037 nM to 80,000 nM and then plotting drugconcentration versus ΔmP. Test well values are normalized to controlreactions run on the same plate (values converted to % of control). IC₅₀values are estimated using nonlinear regression software, fitting afour-parameter one-site dose-response model (XLFit; IDBS, Cambridge,Mass.). Bottom of curve is fixed at 0% of control.

Quality Controls:

To determine the IC₅₀ of an inhibitor, an enzyme concentration that gaveoptimal signal range of 100-200 milli-polarization units is selected.The total fluorescence intensity of each sample well is measured tocalculate the average and standard deviation. If the total fluorescenceintensity of any sample well is not within the range of Average±3SD, themp value of that particular well is discarded.

Using the IMAP procedure described or similarly described above, wescreened a proprietary PDE-focused compound library to identify novelcompounds with nanomolar PDE2 inhibitory activities. The exemplifiedcompounds of the Disclosure (e.g. compounds of Examples 1-22) are testedand shown to generally have an IC₅₀ value of less than 2 μM, majority ofthe compounds having an IC₅₀ value of less than or equal to 250 nM, mostcompounds less than 100 nM, some less than 10 nM. In particular, theIC₅₀ values of Bay 60-7550 and Examples 17, 19, 20, 21 and 22 are shownbelow.

Example PDE2 IC₅₀ (μM) Bay 60-7550 0.001 19 0.073 20 0.012 17 0.028 210.0094 22 0.0059

Example 24 Pharmacokinetic Study in Mice

Mice are given a single oral dose of the compound of Example 22 (10mg/kg, PO) and plasma and brain availability are measured (0.25-4 h)using HPLC and LC-MS using methods analogous to those described in Zhaoet al., J. Chromatogr. B. Analyt. Technol. Biomed. Life Sci. (2005)819(1):73-80 and Appels, N. M., et al., Rapid Commun. Mass Spec. 2005.19(15): p. 2187-92. The experiment shows that the compound of Example 22has good brain access as shown in the table below compared to thepublished standard Bay 60-7550, which has a Cmax of 3 ng/ml; Tmax of0.25 h and a blood to plasma ratio of 0.04 at 10 mg/kg PO.

PK Ex. 22 10 mg/kg Blood/plasma Parameters Description PO Brain Ratio EHalf-life hr 2.4 Cmax (obs) ng/ml 17 1.4 Tmax (obs) hr 2.0 AUC (0-4 hr)ng-hr/ml 50 1.4 (obs area) AUC (area) ng-hr/ml 83 0.9

Example 25 Measurements of cGMP in Mouse Brain In Vivo

Mice are given a single intraperitoneal (i.p.) dose of the compound ofExample 22 (3 mg/kg) or BAY 60-7550 (3 mg/kg) then killed by focusedmicrowave irradiation of the head 15, 30, or 60 min later, as indicatedin FIG. 1. Striatum are dissected from the mouse brains and assayed forlevels of cGMP. Trichloroacetic acid (TCA) is added to tissue samplesfor a final concentration of 5% TCA and the tissue is immediatelysonicated in solution and stored on ice. The sonicated sample iscentrifuged at 15,000×g for 20 min at 4° C. to remove the precipitatedprotein. To extract the TCA, the sample is washed three times in watersaturated ether. The samples are then dried under vacuum (Speedvac,Savant SPD111V) at room temperature and re-suspended in 100 μL EIAbuffer. Both the samples and the cGMP serial diluted standards areacetylated using 0.64 M KOH and 4% acetic anhydride to increase theaffinity of the cGMP antibody. Each sample is tested in duplicate inprecoated assay plates alongside the 8-point cGMP standard dilutions. Inaddition, blank, maximum binding (B₀) and non-specific binding wells areincluded. To all wells containing 50 μL sample or standard, equalvolumes of AChE-linked cGMP and cGMP antibody are added. The plate isincubated at 4° C. for 18 hours. The wells are then washed 5 times withwash buffer. Detection reagent containing acetylthiocholine and2-nitrobenzoic acid is added and the plate is incubated at roomtemperature until the OD of the B₀ wells is at least 0.5 as recorded bythe SoftMax 4.8 software (Molecular Devices, Sunnyvale, Calif.). Eachdata point is converted to % B/B₀ (100*[(sample or standard OD−averagenon-specific binding)/(average B₀−average non-specific binding)]). Thestandards are plotted and fit to a 4-parameter logistic equation (FIG.1). The concentrations of the samples are interpolated from the standardcurve using Microsoft Excel and GraphPad Prizm.

Using the procedure as described or similarly described above, theexperiment shows that the compound of Example 22 increases cGMP levelsin the striatum of mice after systemic dosing compared to Bay 60-7550(See FIG. 1), which shows improvement in brain access of the compound ofExample 22 compared to Bay60-7550.

1. A Compound of Formula I

wherein (i) R₁ is C₁₋₄alkyl (ii) R₂ is selected from the groupconsisting of: H, —OH, halo, C₁₋₄alkyl, C₁₋₄alkoxy, —N(R_(f))(R_(g)),—C(O)N(R_(h))(R_(i)), —C(O)OR_(j), —CN, C₁₋₄alkylthio, heteroaryl,heteroC₃₋₇cycloalkyl or pyrrolidinyl, and aryloxy wherein said aryl isoptionally substituted with one or more halo; (iii) R₃ is H orC₁₋₄alkyl; (iv) R_(a), R_(b), R_(c), R_(d) and R_(e) are independentlyH, halo, —O—C₁₋₆alkyl; (v) R_(f) and R_(g) are independently H,C₁₋₄alkyl or heteroaryl; (vi) R_(h) and R_(i) are independently H orC₁₋₄alkyl; (vii) R_(j) is H or C₁₋₄alkyl; in free or salt form.
 2. Thecompound according to claim 1, wherein the compound is Formula I(i):

in free or salt form.
 3. The compound according to claim 1, wherein: (i)R₁ is C₁₋₄alkyl; (ii) R₂ is C₁₋₄alkoxy; (iii) R₃ is H; (iv) R_(b), R_(c)and R_(e) are H; R_(a) is halo and R_(d) is —O—C₁₋₆alkyl; in free orsalt form.
 4. The compound according to claim 1, wherein the compound isselected from the group consisting of:1-(5-Butoxy-2-fluorophenyl)-8-(4-fluorophenoxy)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(5-Butoxy-2-fluorophenyl)-8-(dimethylamino)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(5-Butoxy-2-fluorophenyl)-3-methyl-8-(pyrrolidin-1-yl)-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(5-Butoxy-2-fluorophenyl)-3-methyl-8-(1H-pyrazol-1-yl)-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(5-Butoxy-2-fluorophenyl)-3-methyl-8-(pyridin-2-ylamino)-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(5-Butoxy-2-fluorophenyl)-8-(ethylthio)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(5-Butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carbonitrile;1-(5-Butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxylicacid; Ethyl1-(5-butoxy-2-fluorophenyl)-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxylate;1-(5-Butoxy-2-fluorophenyl)-N-ethyl-3-methyl-4-oxo-4,5-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxamide;1-(5-Butoxy-2-fluorophenyl)-3-methyl-4-oxo-3a,4-dihydro-1H-pyrazolo[4,3-c][1,5]naphthyridine-8-carboxamide;8-Chloro-1-(2-chloro-5-(cyclopropylmethoxy)phenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(2,5-Dichlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(2-Chlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(2-Chlorophenyl)-3,5-dimethyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(2,5-Dichlorophenyl)-3,5-dimethyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(5-Butoxy-2-chlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(5-Butoxy-2-fluorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;8-Chloro-1-(2,5-dichlorophenyl)-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(5-Butoxy-2-chlorophenyl)-8-chloro-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;1-(5-Butoxy-2-chlorophenyl)-8-methoxy-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;and1-(2-Chloro-5-(cyclobutylmethoxy)phenyl)-8-methoxy-3-methyl-1H-pyrazolo[4,3-c][1,5]naphthyridin-4(5H)-one;in free or salt form.
 5. A pharmaceutical composition comprising acompound according to claim 1, in combination or association with apharmaceutically acceptable diluents or carrier.
 6. A method for thetreatment of a PDE2 mediated disorder comprising administering to asubject in need thereof an effective amount of a compound according toclaim
 1. 7. The method of claim 6, wherein the disorder is selected fromthe group consisting of neurological disorders; cerebrovasculardiseases; spinal muscular atrophy; lateral sclerosis; multiplesclerosis; cognitive disorders; mental deficiency; sleep disorders;psychiatric disorders; factitious disorder; impulse control disorders;mood disorders; psychomotor disorders; psychotic disorders; drugdependence; eating disorders; pediatric psychiatric disorders; mentaland behavioral disorders due to psychoactive substance use;cardiovascular disorder; and pain.
 8. The method of claim 6 wherein thedisorder is selected from the group consisting of: anxiety, depression,autism spectrum disorder, schizophrenia, anxiety and/or depression inautistic and/or schizophrenic patients, and cognitive impairmentassociated with schizophrenia or dementia.
 9. (canceled)
 10. Apharmaceutical composition comprising the compound according to claim 1,in pharmaceutically acceptable salt form.
 11. A pharmaceuticalcomposition comprising the compound according to claim 1, inpharmaceutically acceptable salt form.